Segments Pretax Earnings by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Information by business segment
Net earned premium	$ 641,840	$ 572,248	$ 1,242,403	$ 1,134,860
Other revenue	65,011	71,326	140,898	157,644
Total revenue	706,851	643,574	1,383,301	1,292,504
Loss and LAE	395,305	335,897	760,467	666,643
Other expense	196,989	170,033	357,449	333,245
Total expense	592,294	505,930	1,117,916	999,888
Earnings before income taxes	114,557	137,644	265,385	292,616
North America Property & Casualty [Member]
Information by business segment
Net earned premium	251,430	196,521	460,669	397,855
Other revenue	6,562	4,921	12,664	10,352
Total revenue	257,992	201,442	473,333	408,207
Loss and LAE	149,834	104,737	266,270	208,290
Other expense	70,119	58,150	138,467	115,688
Total expense	219,953	162,887	404,737	323,978
Earnings before income taxes	38,039	38,555	68,596	84,229
Accident & Health [Member]
Information by business segment
Net earned premium	255,663	240,338	510,613	472,481
Other revenue	1,906	3,862	3,919	5,502
Total revenue	257,569	244,200	514,532	477,983
Loss and LAE	186,929	174,139	373,940	344,944
Other expense	40,974	36,032	79,639	70,605
Total expense	227,903	210,171	453,579	415,549
Earnings before income taxes	29,666	34,029	60,953	62,434
International [Member]
Information by business segment
Net earned premium	134,744	135,060	271,121	263,904
Other revenue	914	855	1,922	1,831
Total revenue	135,658	135,915	273,043	265,735
Loss and LAE	58,275	56,518	119,718	112,832
Other expense	51,881	49,345	99,192	95,820
Total expense	110,156	105,863	218,910	208,652
Earnings before income taxes	25,502	30,052	54,133	57,083
Investing [Member]
Information by business segment
Net earned premium	0	0	0	0
Other revenue	55,311	61,343	121,979	138,395
Total revenue	55,311	61,343	121,979	138,395
Loss and LAE	0	0	0	0
Other expense	0	0	0	0
Total expense	0	0	0	0
Earnings before income taxes	55,311	61,343	121,979	138,395
Corporate & Other [Member]
Information by business segment
Net earned premium	3	329	0	620
Other revenue	318	345	414	1,564
Total revenue	321	674	414	2,184
Loss and LAE	267	503	539	577
Other expense	34,015	26,506	40,151	51,132
Total expense	34,282	27,009	40,690	51,709
Earnings before income taxes	$ (33,961)	$ (26,335)	$ (40,276)	$ (49,525)